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https://issues.apache.org/jira/browse/HADOOP-12603?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15032152#comment-15032152
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Alan Burlison commented on HADOOP-12603:
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Ahah, that's the bit of the jigsaw I was missing - yes I only checked files.
However I think your supposition is correct - accessing a dir is accessing a
dir, even if it's done through a symlink so atime will be updated, and POSIX
says this about the timestamp resolution of the utimes() syscall:
{code}
accuracy is only to the microsecond, not nanosecond, and rounding towards the
nearest second may occur.
{code}
I think it's therefore safest to assume rounding will happen. If you use the
futimens() or utimensat() syscall then you should get nanosecond-accurate times
but to be maximally portable I think you need to assume the JVM will use
utimes() and will therefore only be microsecond-accurate at best, and may round
up to the nearest second.
I think rather than special-casing the test for specific platforms it should
just be modified to check for the POSIX semantics, as anything else is
non-portable.
> TestSymlinkLocalFSFileContext#testSetTimesSymlinkToDir occasionally fail
> ------------------------------------------------------------------------
>
> Key: HADOOP-12603
> URL: https://issues.apache.org/jira/browse/HADOOP-12603
> Project: Hadoop Common
> Issue Type: Bug
> Reporter: Wei-Chiu Chuang
> Assignee: Wei-Chiu Chuang
> Labels: solaris, windows
> Attachments: HADOOP-12603.001.patch
>
>
> I have observed this test failure a few times in the past. When it fails, the
> expected access time (of the file link) is always 1000 less than the actual
> access time.
> Error Message
> {noformat}
> expected:<1448478654000> but was:<1448478655000>
> {noformat}
> Stacktrace
> {noformat}
> java.lang.AssertionError: expected:<1448478654000> but was:<1448478655000>
> at org.junit.Assert.fail(Assert.java:88)
> at org.junit.Assert.failNotEquals(Assert.java:743)
> at org.junit.Assert.assertEquals(Assert.java:118)
> at org.junit.Assert.assertEquals(Assert.java:555)
> at org.junit.Assert.assertEquals(Assert.java:542)
> at
> org.apache.hadoop.fs.SymlinkBaseTest.testSetTimesSymlinkToDir(SymlinkBaseTest.java:1391)
> at
> org.apache.hadoop.fs.TestSymlinkLocalFS.testSetTimesSymlinkToDir(TestSymlinkLocalFS.java:233)
> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> at
> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
> at java.lang.reflect.Method.invoke(Method.java:606)
> at
> org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
> at
> org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
> at
> org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
> at
> org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
> at
> org.junit.internal.runners.statements.FailOnTimeout$StatementThread.run(FailOnTimeout.java:74)
> {noformat}
> Standard Output
> {noformat}
> 2015-11-25 19:10:55,231 WARN fs.FileUtil (FileUtil.java:symLink(813)) -
> Command 'ln -s
> /testptch/hadoop/hadoop-common-project/hadoop-common/target/test/data/4/vae1ng5t75/test1/file
>
> /testptch/hadoop/hadoop-common-project/hadoop-common/target/test/data/4/vae1ng5t75/test2/linkToFile'
> failed 1 with: ln: failed to create symbolic link
> '/testptch/hadoop/hadoop-common-project/hadoop-common/target/test/data/4/vae1ng5t75/test2/linkToFile':
> No such file or directory
> 2015-11-25 19:10:56,212 WARN fs.FileUtil (FileUtil.java:symLink(813)) -
> Command 'ln -s
> /testptch/hadoop/hadoop-common-project/hadoop-common/target/test/data/4/vae1ng5t75/test1/file
>
> /testptch/hadoop/hadoop-common-project/hadoop-common/target/test/data/4/vae1ng5t75/test1/linkToFile'
> failed 1 with: ln: failed to create symbolic link
> '/testptch/hadoop/hadoop-common-project/hadoop-common/target/test/data/4/vae1ng5t75/test1/linkToFile':
> File exists
> {noformat}
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